Despite recent efforts to transform its reputation, the budget airline was one of the worst-performing brands overall in Siegel+Gale's 2014 simplicity index.

In a survey of over 12,000 customers in eight countries, Ryanair was named the second worst-ranked brand, based on ease of customer use of a company's products, services, interactions and communications

Primary customer complaints against the airline were Ryanair's badly designed website and poor customer service that 'leaves the onus on the customer.'

The airline's app was also named a major cause for headaches, with many having difficulty in downloading mobile boarding passes.

'The pricing is far too complicated and isn’t put forward honestly,' one respondent said of the airline. 'There’s so many variations and hidden charges on flights and options, it’s hardly worth the hassle,' said another.

Other customer criticised that the airline is 'too strict and inflexible on luggage allowances,' and another notes that 'what appear to be amazing offers turn out to be a lot worse off on closer inspection.'

In the UK, 1,700 survey respondents ranked the airline 114th, up ten places in the index from last year. Ryanair placed above brands including AXA, Blackberry, BUPA and E.ON for simplicity.

Despite once dismissing disgruntled passengers as 'stupid', Ryanair CEO Michael O'Leary told MailOnline Travel this week: 'We should have been nicer to customers earlier than we have been'.

On the 'Always Getting Better' programme implemented by the airline, he said: ‘This is a change. We have just completed the first year, I think we have two more years of the program to roll out where you’re going to see more and more focus on improving the experience and actively listening to customers and trying to provide them with the services they’re looking for.

‘As I said myself if I had known being nicer to our customers was going to work so well I would have done it years ago.’

Liana Dinghile, Group Strategy Director EMEA at Siegel+Gale said: 'Despite Ryanair’s investment over the past 12 months in simplifying its website, mobile app and customer service to correspond with its "Low fares. Made simple" strapline, it seems that the company is ultimately still falling short of its promise.

'Respondents in our study found Ryanair’s booking system in particular "complex" and "confusing," and 38 per cent said they would be willing to pay more for simpler experiences.

'People crave simplicity, and Michael O’Leary would be wise to keep this in mind as he continues to address the repositioning of the company this year. Particularly as Easyjet has climbed 32 places in the same time frame!'

In the global industry ranking for simplicity of use, the travel sector did not fare well. Hotels ranked the highest in 11th place overall, while booking agents and air travel brands placed 13th and 15th overall, respectively.